2:  #include <petsc/private/taolinesearchimpl.h>

  4: static PetscErrorCode TaoLineSearchDestroy_Unit(TaoLineSearch ls)
  5: {
  8:   PetscFree(ls->data);
  9:   return(0);
 10: }

 12: static PetscErrorCode TaoLineSearchSetFromOptions_Unit(PetscOptionItems *PetscOptionsObject,TaoLineSearch ls)
 13: {
 16:   PetscOptionsHead(PetscOptionsObject,"No Unit line search options");
 17:   PetscOptionsTail();
 18:   return(0);
 19: }

 21: static PetscErrorCode TaoLineSearchView_Unit(TaoLineSearch ls,PetscViewer viewer)
 22: {
 24:   PetscBool      isascii;

 27:   PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii);
 28:   if (isascii) {
 29:     ierr=PetscViewerASCIIPrintf(viewer,"  Line Search: Unit Step.\n");
 30:   }
 31:   return(0);
 32: }

 34: static PetscErrorCode TaoLineSearchApply_Unit(TaoLineSearch ls,Vec x,PetscReal *f,Vec g,Vec step_direction)
 35: {
 37:   PetscReal      ftry;
 38:   PetscReal      startf = *f;

 41:   /* Take unit step (newx = startx + 1.0*step_direction) */
 42:   VecAXPY(x,1.0,step_direction);
 43:   TaoLineSearchComputeObjectiveAndGradient(ls,x,&ftry,g);
 44:   PetscInfo1(ls,"Tao Apply Unit Step: %4.4e\n",1.0);
 45:   if (startf < ftry){
 46:     PetscInfo2(ls,"Tao Apply Unit Step, FINCREASE: F old:= %12.10e, F new: %12.10e\n",(double)startf,(double)ftry);
 47:   }
 48:   *f = ftry;
 49:   ls->step = 1.0;
 50:   ls->reason=TAOLINESEARCH_SUCCESS;
 51:   return(0);
 52: }

 54: /*@C
 55:    TaoCreateUnitLineSearch - Always use step length of 1.0

 57:    Input Parameters:
 58: .  tao - Tao context

 60:    Level: advanced

 62: .keywords: Tao, linesearch
 63: @*/
 64: PETSC_EXTERN PetscErrorCode TaoLineSearchCreate_Unit(TaoLineSearch ls)
 65: {
 67:   ls->ops->setup = 0;
 68:   ls->ops->reset = 0;
 69:   ls->ops->apply = TaoLineSearchApply_Unit;
 70:   ls->ops->view = TaoLineSearchView_Unit;
 71:   ls->ops->destroy = TaoLineSearchDestroy_Unit;
 72:   ls->ops->setfromoptions = TaoLineSearchSetFromOptions_Unit;
 73:   return(0);
 74: }